Immunohistochemical evidence for the existence of novel mammalian neuropeptides related to the Hydra GLW-amide neuropeptide family

On the origin of appetite: GLWamide in jellyfish represents an ancestral satiety neuropeptide

Food intake is regulated by internal state. This function is mediated by hormones and neuropeptides, which are best characterized in popular model species. However, the evolutionary origins of such feeding-regulating neuropeptides are poorly understood. We used the jellyfish Cladonema to address this question. Our combined transcriptomic, behavioral, and anatomical approaches identified GLWamide as a feeding-suppressing peptide that selectively inhibits tentacle contraction in this jellyfish. In the fruit fly Drosophila, myoinhibitory peptide (MIP) is a related satiety peptide. Surprisingly, we found that GLWamide and MIP were fully interchangeable in these evolutionarily distant species for feeding suppression. Our results suggest that the satiety signaling systems of diverse animals share an ancient origin.

Insight into the molecular and functional diversity of cnidarian neuropeptides

Cnidarians are the most primitive animals to possess a nervous system. This phylum is composed of the classes Scyphozoa (jellyfish), Cubozoa (box jellyfish), and Hydrozoa (e.g., Hydra, Hydractinia), which make up the subphylum Medusozoa, as well as the class Anthozoa (sea anemones and corals). Neuropeptides have an early evolutionary origin and are already abundant in cnidarians. For example, from the cnidarian Hydra, a key model system for studying the peptides involved in developmental and physiological processes, we identified a wide variety of novel neuropeptides from Hydra magnipapillata (the Hydra Peptide Project). Most of these peptides act directly on muscle cells and induce contraction and relaxation. Some peptides are involved in cell differentiation and morphogenesis. In this review, we describe FMRFamide-like peptides (FLPs), GLWamide-family peptides, and the neuropeptide Hym-355; FPQSFLPRGamide. Several hundred FLPs have been isolated from invertebrate animals such as cnidarians. GLWamide-family peptides function as signaling molecules in muscle contraction, metamorphosis, and settlement in cnidarians. Hym-355; FPQSFLPRGamide enhances neuronal differentiation in Hydra. Recently, GLWamide-family peptides and Hym-355; FPQSFLPRGamide were shown to trigger oocyte maturation and subsequent spawning in the hydrozoan jellyfish Cytaeis uchidae. These findings suggest the importance of these neuropeptides in both developmental and physiological processes.

The Importance of GLWamide Neuropeptides in Cnidarian Development and Physiology

The peptide-signaling molecules (<50 amino acid residues) occur in a wide variety of invertebrate and vertebrate organisms, playing pivotal roles in physiological, endocrine, and developmental processes. While some of these peptides display similar structures in mammals and invertebrates, others differ with respect to their structure and function in a species-specific manner. Such a conservation of basic structure and function implies that many peptide-signaling molecules arose very early in the evolutionary history of some taxa, while species-specific characteristics led us to suggest that they also acquire the ability to evolve in response to specific environmental conditions. In this paper, we describe GLWamide-family peptides that function as signaling molecules in the process of muscle contraction, metamorphosis, and settlement in cnidarians. The peptides are produced by neurons and are therefore referred to as neuropeptides. We discuss the importance of the neuropeptides in both developmental and physiological processes in a subset of hydrozoans, as well as the potential use as a seed compound in drug development and aspects related to the protection of corals.